Wiring question - power seats into an early 911

[Christien]

I'm installing a 944 power driver's chair into my 72. I've run a fused wire directly from the battery, and ground from a chair mount bolt. I've cut the wiring plug off the end of the wires from the chair and proceeded to hook the wires up. I first connected the ground, then as soon as I touched the positives, I got a small spark and blew the fuse. Not knowing which wire from the chair is positive and which is negative, I reversed the ground connection then connected the positive. Same result.

What am I doing wrong? Sorry if this is an idiotic question - electrical is definitely my weak point.

[RSBob]

A better question is why you feel compelled to install a heavy electrical seat in an early car. It's not a Buick.

[Christien]

It weighs less than the original Recaro that was in there, and they were an excellent price for the pair. Good enough?

[nineball]

what size wire and fuse? i would suggest you use 12g and 20a. if the wire is arcing and the fuse is blowing as soon as you make a connection it sounds like there is a problem with the seat. try using a spare battery on a bench to test the seats and see if they actually work.

[Grady Clay]

Christien,

Search around and post the wiring diagram (or a link) for the 944 seats.
We can better help then.

DC electric motors have a large (‘inrush’) starting current.
This is significantly more than the ‘running current’.
They must be fused appropriately.

What are the wire colors for the pair you tried to use?

Best,
Grady

[Christien]

I'm using 20 amp fuses and 12 gauge wiring. I hooked it up, unfused, to a power pack to test. Not knowing the polarity, I tried it both ways. One way I got smoke at the wiring connection, very quickly, maybe 1 second. The other way I got nothing. No smoke or spark, but no power to the motors, either. The guy I bought them from said they worked, though it's possible they're dead.

Grady: I'm not working from a wiring diagram - there was only one wire hanging out, with the plug on the end, so I assumed it was the power wire. I did the opposite of this several years ago, 911 power seat into a 944, and my memory was that it was very simple and obvious.

Both wires coming out of the seat are black, inside a black sheath.

Here are pics of the wires, motors, and plug that I cut off:

[Grady Clay]

Christien,

I thought I had a pair of electric 944 seats. They were sold to me as that ($20/pair).
(They have been used for video games for a few decades.)

(Chris, age 12 in '97. I can tell by the size 12 shoes.)



However, as I looked I see the 3-point MB star on some connectors ("B").







I don’t think this will help – d**n!

We need a wiring diagram and year of the seats.

Best,
Grady

[bkreigsr]

Christian, on my RSA seats, I was able to bring a hot wire from the fuse block to the red leads in the newer seat. I ran a (brown) ground back to the ground stud on the lower drivers side under the cowl. I spliced them both and jumped over the tunnel to power the passenger side. (to the purists - the original hounds-tooth seats are in my attic)
fwiw, I bench-tested all the connections before install to see which reds needed power.
Have you considered that the seat control switch is shorted?
Bill K

[Christien]

Ok, I got it sorted out. I was using the wrong wires. I have no idea what those wires are. Maybe they piggyback the electricity over to the passenger side.

The correct plug is on the topside of the brass plate marked C in Grady's picture. It has 4 male prongs, and the appropriate terminals are the near two (i.e. left two if the chair were upright). Trial and error had it working inside of a few minutes. Now I just need to figure out how to get a soldering gun in there

[Bob Kontak]

Pretty sure the three pronged unit is for the seatbelt warning system.